Conventionally, there have been cases where a stent which is formed in the shape of a hollow cylinder having a multiplicity of openings in its side wall, which is made from metallic wire or the like, and which can be expanded in a living body lumen, such as blood vessel, bile duct, trachea, esophagus, urethra, etc., is used for improvement of a lesion part (stenosed part or obliterated part) generated in the living body lumen.
For example, a stent having a self-expanding function (self-expandable stent) is delivered into a living body lumen while being held in a distal portion of a delivery catheter having an outer tube disposed in the periphery of an inner tube, in the state of being compressed and contained in the gap between the inner tube and the outer tube. Then, the outer tube is retracted proximally to cause the stent to be released and expanded, whereby the stent can be put indwelling in a desired part in the living body lumen.
Such a stent delivery system having a stent and a catheter is disclosed, for example, in JP-T-2010-517735, wherein an outer tube is disposed in the periphery of an inner tube, and a stent is disposed in the state of being contained in a gap between the inner tube and the outer tube in the vicinity of a distal portion of the stent delivery system. In this system, by operating an operating unit at the proximal end, the outer tube is withdrawn toward the proximal side, whereby the stent on the distal side is smoothly released into and expanded in the living body lumen.
In the stent delivery system described in JP-T-2010-517735 mentioned above, at the time when the distal ends of the inner tube and the outer tube are advanced into the living body lumen such as a blood vessel, the blood or a contrast agent used for imaging of the inside of the living body lumen may penetrate toward the proximal side of the stent delivery system via the inner tube and the outer tube. If such blood or contrast agent having a viscosity stagnates in the gap between the inner tube and the outer tube, it may cause a sliding resistance at the time of movement of the outer tube for releasing the stent, thereby making it impossible to smoothly perform the stent indwelling operation. In addition, there is a fear that the blood or contrast agent could flow through the gap between the inner tube and the outer tube into an operating unit, thereby obstructing the operation of the operating unit.